The invention concerns a process and a device for hot rolling in a hot strip mill or in Steckel mills, where slabs are rolled out to near-net strip in one or more roughing stands.
The near-net strip produced in this way should be straight, i.e., it should have only slight strip cambering and should have no wedging over the width of the strip. It is the task of the roughing stands not merely to maintain the geometry of the near-net strip but rather to improve it in a systematic way, since the slabs entering the stands may already be affected by wedging or cambering. A change in the geometry of the near-net strip is possible primarily in the first passes, since the slab thickness is still large relative to the width, so that transverse flow of material in the roll gap is possible.
The rolling of hot strip is sometimes attended by variably large drafts per pass over the length of the roll gap (over the width of the strip), which can be attributed to variations in the quality of the rolling stock, to variations in the roll gap itself, or to the geometry of the entering rolling stock. These variably large drafts per pass then lead to lateral deflections and shifts of the rolling stock in the stand and to lateral curvature of the exiting hot rolled strip.
Various processes and devices are known for automatically controlling the advancement of the strip and for correcting the curvature of the exiting hot rolled strip.
For example, DE 197 04 337 A1 proposes a process for automatically controlling the advancement of rolled strip as it passes through a rolling train, where the position of the rolled strip relative to the center line of the rolling train is measured in at least one rolling stand, and the measured values are used for automatically adjusting the rolling force distribution in the longitudinal direction of the rolls of this rolling stand to obtain a desired set position. This measure results in advancement of the rolled strip that is very nearly symmetrical to the center line, but it may also lead to the development of wedging of the rolled strip.
DE 43 10 547 C2 discloses another possible process for preventing lateral bending of the rolled strip, which is moved continuously through a roughing train with an edging mill for influencing the width of the strip and a horizontal rolling mill for influencing the thickness of the strip, in which hydraulically adjustable lateral guides are installed along the sides of the rolled strip. The lateral guides are arranged upstream and downstream of the edging mill and control the lateral shifting of the rolled slab, and they allow unhindered entrance and exit of the rolled strip by alternate narrowing of the distance between the lateral guides.
DE 31 16 278 C2 discloses a device for controlling the position of the strip travel, especially during finish rolling, in which guide strips arranged alongside the rolled strip have bending bars with guide rollers, which are pressed laterally against the rolled strip. The automatic position control system of these rollers has a superimposed automatic pressure control system, which, when disturbing forces arise that exceed a preset value, brings about a shift of the guide strips or guide rollers in the opening direction.